Corrugated steel pipe sections can be used to form pipeline drainage systems along or beneath highways, or for various other construction projects where diversion of water flow or drainage of runoff is required. Depending upon the size and nature of the project, the dimensions of the corrugated steel pipe that are used to form the drainage system may vary. Steel corrugated pipe sections of this type range in diameter from 36" to 144", are made in lengths of up to 24', and have a thickness of 0.168", or 8 gauge. High strength, helically corrugated pipes of this type may be made from galvanized steel or aluminized steel and lined on the inside with a machine applied, dense, high strength concrete lining to a minimum of 1/8 inch thickness above the crest of the corrugation.
Couplings for joining sections of pipe must meet the same performance requirements as the individual sections of pipe. The connection must be soil tight and although the joint need not be watertight, it must not permit water to flow out at such a volume and velocity as to cause undue settling or erosion of the soil surrounding the pipe. If the pipe is to be situated below the water table, the pipe joints must also preclude the ingress of water. Furthermore, pipe joints must be sufficiently rigid to maintain the proper alignment of the joined pipe sections. Varying pressures on the ground above the joined pipe sections must not adversely affect this desired alignment.
U.S. Pat. No. 3,501,179, in the name of Jerold H. Boynton et al, provided a coupling which met these performance requirements for joining sections of helically corrugated pipe having an angle of connection of 180.degree., or a straight line connection. Boynton disclosed a sleeve type coupling sized to receive the ends of the pipe sections to be joined. The Boynton coupling also provided annular corrugations of substantially the same pitch, size and depth which were seated on an annular corrugation at the end of each of the pipe sections.
The Boynton patent has proved more than adequate for straight line connections. However, due to ground contour and the accommodation of optimum drainage routes, most pipeline applications require a number of angled connections between pipe sections. The problems normally encountered in joining sections of helically corrugated pipe become further complicated when the pipe sections must be connected at an angle.
In the past, angled connections have been made at the job site by a time consuming process requiring substantial cutting and welding of each of the separate pipe sections. The separate sections of pipe must be repeatedly re-oriented to access the circumferential edges of the pipes in order to obtain a proper seal about the entire circumferential surface of connection. This re-orientation often requires some longitudinal movement of one pipe section with respect to the other, a difficult maneuver when connecting pipe sections that have a large diameter or a paved bottom. Regardless of the dimensions or composition of the pipe section, a connection process of this type results in delay, additional expense and becomes increasingly difficult under adverse weather conditions.
Couplings formed in the field in this manner will vary according to a number of factors, including the angle of connection, the width of the pipe sections, the depth of the pipeline, access to the circumferential surface of connection, the surrounding soil conditions, etc. Due to variation of these factors along the length of any given pipeline, the quality of the connections along the pipeline will vary, thus frustrating attempts to provide uniform structural integrity. Moreover, variations in the quality of connections along the route of the pipeline results in inconsistencies in the pipeline's ability to withstand wear and tear, thereby frustrating troubleshooting and compounding difficulties associated with subsequent maintenance.
In view of the disadvantages associated with present methods and devices for coupling pipe sections at varying angles of connection, there is a definite need to develop means for forming consistent, high quality connections of this type that do not require multiple cuts and welds at the job site, nor difficult and time consuming maneuvering of the pipe sections to achieve the orientation necessary for performing such cuts and welds.